Apparatus for the electrolysis of aqueous solutions.



M. I IUTH. I

APPARATUS FOR THE BLEOTROLYSIS 0P AQUEOUS SOLUTIONS.

APPLICATION FILED JAN- 5. 1909.

5,109, Patented Sept. 28, 1909 WWWWWWWW/ MAX min, or emmmmENBuR-e, NEAR BERLIN, GERMANY, Asszsnon TO SIEMENS & naiisnn A. e-., or BERLIN, GERMANY, A oonrona'ri'onor GERMANY.

APPARATUS F03, THE ELEGTROiJYSIS 0 AQUEOUS SOLUTIONS.

Specificationnf Letters Patent. P tented Sept. 28, race.

application filed January 5, 1-909. Serial No. 470,880.

Charlotten'burg, near Berlin, Germany, have invented certain new and useful Improvements in Apparatus for the Electrolysis of Aqueous Solutions, of which the following account of impurltles passing lnt'o the elecis a specification.

The present invention relates to'apparatus for the electrolysis of aqueous solutions, such as solutions of zinc sulfate, nitrate of copper, if sodium chlorid or the like, which may also 5 contain free acid.

When electrolyzing aqueous solutions in 3 general and particularly aqueous solutions of salts, it is preferable for the anode to consist of a material. which cannot be attacked: roposed'i to make the anode of peroxid of cad for. such purposes. The employment of such anodes has also proved successful, but the- I employment of these peroxid of lead anodes is limited, having regard to the employment Also it isfrequently disadvantageous when lea-d ions chemically. It has already been heretofore int-he form of rods.

pass into the solution from the peroxid of lead on'accoun-t of reduction which occurs under certain circumstances.

vention instead of peroxid of lead, peroxid of manganese is used as anode in a solid form which is obtained artificially. Crystalline peroxid of manganese conducts electric does take place under certain circumstances,

I only manganese ions pass into the solution and these have no injurious effect on the deposition of metal at the cathode.

It has already been attempted to employ peroxid of manganese electrodes, namely, for

example, in the form of a sheet of platinum coated electrolytically with amorphous peroxid of manganese. 'Peroxi-d of manganese electrodes made in this manner cannot be employed as anodes, however, since this peroxid of manganese has the property of being converted in dilute sulfuric acid by the electric current into higher degrees of oxidation which are soluble in water. The highest degree of oxidation of manganese, permanganic acid, is most readily formedin this manner. Further, it has been proposed to use natural manganese ore in the form of pieces or lumps and to. conduct the current to these anodes by means of carbon rods. But these anodes also have a number of disadvantages. Namely, when electrolyzing aqueous solutions by means of so-c'alled insoluble anodes disadvantages ,frequentlyoccur on trolyte from the anode material owing to chemical or anodic solvent actions. Consequently, as a rule, 'the cathode products are of inferior quality and also the anode ma terial is destroyed more rapidly. Such results are particularly noticeable in the electrolysis of zinc sulfate solutions, in which any metal which is more electronegative than zinc must be carefully prevented from passing into the electrolyte. Natural manganese v Now in accordance with the present in- I been found that crystalline peroxid of manganese, such as is formed by heating manganese nitrate or in similar manner, possesses suliicient mechanical strength to be employed in solid form and without .supporting sheet metal insertions or the like. Further, it has been found that this crystalline peroxid of manganese is either not oxidized higher at all or only to a very insignificant extent in sulfate solutions and the like during the electrolysis, for example when used as anode in dilute sulfuric acid. In so far as oxidation does occur at all the same takes place only when freshly made electrodes are first used, and is to be attributed to the freshly made peroxid "of manganese electrodes containing amorphous peroxid of manganese or manganese of other degrees. of oxidation, if to only a small extent. But in themselves peroxid of manganese electrodes are to be looked upon as anodes which cannot be attacked, that is to say oxygen escapes at the anode when sulfuricacid is electrolyzed for example, and

at most a very small fraction of the electric the anode. Further, under certain circumstances it is advantageous to impre ate the peroxid of manganese electrode with poreclosing, means which cannot be attacked, such as ceresin, paraflin or the like. The electrolyte does not then penetrate into the pores of the electrode, so that consequently the place of contact is protected from the action of the electrolyte, and on the other hand the electrolyte is also protected from impurities. Under certain circumstances it suffices to treat in this manner only one strip of the electrode a few centimeters broad bounding the place of contact.

The peroxid of manganese electrode suitable for the present process can be made, for example, by pure nitrate of manganese being heated to 150 to 200 C. in molds which are attacked neither by the molten mass produced nor b the gases which are formed. The peroxi of manganese separates as a solidcoherent mass, it bein given the form of the vessel which is us duration of the heating depends, of course, on the size of the electrodes which are to be produced. Under-certain circumstances it may be preferable to press crystalline peroxid of manganese into molds mechanically, in which case nitrate of manganese may be used as a bindin agent, the mass being then heated if desire In this manner, besides pure crystalline peroxid of manganese, old',

already used electrodescan be worked up after suitable preparation for employment as anodes. Thus it is possible to obtain eroxid of manganese both in rods an in plates according to the requirements in each instance.

Owing to this fact and owing to peroxid of manganese electrodes when employed as anodes having the advantage that they can send only manganese ions into solution as mentioned above, in the event of reduction occurring such anodes can be used with advantage for the electrolysis of zinc from aqueous sulfate solutions. For as no metal which is more electronegative than zinc can pass into the solution, even if the anode is attacked such electrolysis will succeed. As

one important advantage of the process it has been found that when pure massive per oxid of man anese is em loyed as anode and when in ad ition care 1s taken that metal ions do not gov into solution from theplaces of contact, a concentration of acid up to over 10% free sulfuric acid can be worked The drawing a trough containing the electrodes described before. In this drawing a represents the trough containing the electrolyte e.

0 represents the perox1d of manganese electrodes to the upper end of which carbon bindings b are fastened.

d represents the cathode.

What I claim as my invention and desire to secure by Letters Patent is:

1. In an apparatus for the electrolysis of aqueous solutions such as zinc sulfate solutions or solutions of other sulfates, an anode consisting of massive, artificially produced peroxid of manganese.

2. In an apparatus for the electrolysis of aqueous solutions such as zinc sulfate solutions or solutions of other sulfates, an anode consisting of massive, artificially produced consisting of massive,.artificially produced peroxid of manganese coated with ceresin.

4. The herein described process of producing massive peroxid of .manganese anodes for electrolyzing aqueous solutions which consists in heating pure nitrate of manganese in molds.

5. The herein described process of producing massive peroxid of manganese anodes for electrolyzing aqueous solutions which consists in mixlng' crystalline manganese with a binding agent, 1n pressing the mixture thus obtained into molds and heatin the same therein.

6. T e herein described process of producing massive peroxid of manganese anodes for electrolyzing aqueous solutions which consists in mixing crystalline peroxid of manganese with nitrate of manganese, in pressing the mixture thus obtained into molds and heating the same therein, as set forth.

In testimony whereof I have signed my name to this specification in the presence of two witnesses.

MAX HUTH.

Witnesses HENRY HASPER, WOLDEMAR HAUPT.

peroxid of 

